Evaluation of Disease Resistance in Selectively Bred Channel Catfish (Ictalurus punctatus) and Hybrid Catfish (Channel Catfish ♀ x Blue Catfish (I. furcatus) ♂)

Abstract

Selectively bred channel catfish (Ictalurus punctatus) and hybrid catfish (channel catfish ♀ x blue catfish (I. furcatus) ♂) were evaluated for resistance to channel catfish virus (CCV) and Flavobacterium covae (FC). In the CCV challenge, survival following CCV exposure varied significantly among families. Overall analysis showed slightly higher resistance for the hybrid catfish. Blue catfish paternal effects were more impactful than channel catfish maternal effects. These results contradicted earlier studies that indicated the resistance of hybrid catfish to CCV was less than or equal to channel catfish. Two FC challenges were conducted, one high dose and one low dose, resulting in extremely rapid and slower mortality, respectively. In the high dose challenge, overall survival fell below 10 % within 72 h, and channel catfish families had longer survival than the hybrid catfish (mean 19.9 h vs 16.8 h; log rank p = 0.01), Family effects were also observed (p < 0.05). In the low dose trial, median survival reached the 176 h study maximum for all families, and channel catfish still averaged longer survival than hybrid catfish (157.4 h vs 138.3 h; p = 0.056). These findings contradict earlier reports that hybrid catfish are more resistant to columnaris than channel catfish (Arias et al., 2012). Genotype-environment interactions may occur due to strain differences in the pathogen, F. covae and/or the confined conditions of the experiments potentially causing more stress on the hybrid catfish leading to greater disease susceptibility in this specific challenge environment.